Exchange graphs and $g$-vectors of surface rigid algebras

Abstract

We classify the connected components of support $τ$-tilting graphs of surface rigid algebras associated with partial tagged triangulations of punctured marked surfaces with nonempty boundary. For a connected algebra, the graph is disconnected if and only if the algebra is weakly symmetric, has at least two simple modules, and has Cartan rank one. In this case, it has exactly two connected components. For every nonzero $τ$-rigid pair over a connected surface rigid algebra, the graph of $τ$-tilting completions is connected. More generally, we classify the completion components for an arbitrary surface rigid algebra and a fixed $τ$-rigid pair. For partial tagged triangulations with all endpoints at punctures, we express the Cartan matrix and $g$-vectors by signed endpoint data. We prove that $τ$-tilting finiteness is equivalent to positive definiteness of the Cartan matrix. In the finite case, we determine the primitive $g$-vector ray generators in endpoint coordinates. Trees give type A, and a criterion on the original partial tagged triangulation distinguishes types D and C in the unicyclic case.